The invention relates to an oil pan module for internal combustion engines, for example those used for driving motor vehicles.
Oil pans used for internal combustion engines that drive motor vehicles are subject, first of all, to high sealing requirements that must be satisfied over the entire service life of the oil pan. During their entire service life, oil pans must resists all anticipated mechanical and thermal stresses over a wide temperature range. The operation of the internal combustion engine heats up the oil pan rapidly from two-digit subfreezing outdoor temperatures to temperatures in the range of about 130xc2x0 C.; hence, the oil pan must be able to withstand the mechanical strains caused by such heat-up.
Moreover, oil pans must also possess corrosion resistance and be resistant to chemical attack by all media commonly encountered in the motor vehicle field. This, first of all, means hot motor oil. Motor oil that has already been used in the internal combustion engine for an extended length of time can attain a pH of 4.5 which is in the acidic range. Other corrosive stresses arise from possible contact with media such as fuel, brake fluid, superheated steam used for engine washing, as well as salt on the outside of the oil pan. The requirements placed on the oil pan component can be found in the specifications supplied by motor vehicle manufacturers. They include, for example, a heat resistance of xe2x88x9240xc2x0 C. to +150xc2x0 C., ability to withstand a continuous heat load of 130xc2x0 C. and resistance to oils, fuels, cold cleaners, salt water and cooling water. Also required is mechanical resistance to common engine vibrations taking into account the fastening screws and the fact that the engine is disposed above the oil pan. The weight of the engine plus the drive train can reach up to 1700 kg. It is required that the fastening points be constructed of an appropriate plastic material and that the sealing element be integrated for certain uses, for example for use of oil pans in trucks, said sealing element being required to last 1 million kilometers assuming simultaneous aging resistance of the construction material used below the sealing element and the absence of condensation phenomena. The oil pans of passenger vehicles must also be resistant to impact stresses encountered when the vehicle passes over a curbstone.
These requirements are met by oil pans made of sheet metal or die-cast aluminum. Also known are hybrid oil pans in which the actual oil pan consists of a thermoplastic polymer reinforced by metallic or plastic elements to increase its mechanical strength. Such an oil pan is known from European Patent EP-0 952 513 A2. In this case, an outer layer of a metallic grid, particularly one made of light-weight metal, or of a plastic with similar strength characteristics is combined with a thin-walled shell.
EP 0 872 632 A1 discloses an oil pan for internal combustion engines which is disposed beneath the crankcase. The oil pan has a double wall consisting of an inner and an outer shell made of thermoplastic polymer, the outer shell being disposed in the lower part of the oil pan and ribs being provided between the inner and the outer shell, said ribs being molded onto the inner and/or outer shell and their height and separation being determined by locally prevailing stress conditions. The inner and outer shell are joined to each other by an appropriate joining method.
German patent DE 197 35 445 C2 discloses a plastic oil pan for engines or gears and which comprises an integrated suction and/or pressure oil filtration, The oil filter medium is disposed in the oil pan, and part of the oil pan forms the bottom of an oil filter housing. The plastic half-shell forms a cover for the oil filter housing, the oil filter medium being held between the oil pan and the plastic half-shell.
DE 196 44 645 A1 discloses an oil pan for an internal combustion engine in which the oil pan is designed as a multifunction component. Integral with the oil pan are an oil pump, an oil filter accessible from the outside, an oil-water heat exchanger, temperature controller, oil dipstick attachment, oil filling tube and possibly even a crankcase venting valve.
Considering the described prior art, the object of the invention is to extend the functionality of plastic engine components used to replace engine components made of metal.
According to the invention, this objective is reached by making the oil pan module out of a thermoplastic polyamide-based polymer reinforced with fillers, such as glass fibers and/or mineral matter.
According to the invention, an oil pan of this type is fabricated by a one-component or multicomponent injection-molding process in which polyamide-based thermoplastic materials are used.
The oil pan module can be made of a high-impact polyamide. Depending on requirements placed on the oil pan module, which are stated, for example, in the specifications of an automobile manufacturer, the oil pan module can be reinforced by incorporating into the thermoplastic material fillers such as glass fibers or mineral matter.
In another embodiment of the invention, a metallic surge sheet in the form of an insert is integrated into the oil pan module of the invention. The surge sheet can be connected to the oil pan module by means of appropriate fasteners such as screws or snaps, and together with said module is fastened to the internal combustion engine beneath the crankcase. To increase the mechanical stability of the oil pan module and to stiffen it, said module is provided with external ribs injection-molded onto it, and on its inside, which holds the lubricant supply, with longitudinal and transverse dividers. This has a favorable effect on the mechanical strength and vibration characteristics of the oil pan module of the invention and results in more uniform temperature distribution so that strains in this component induced by nonuniform heating are prevented.
Integrated with the oil pan module is an electric oil pump disposed parallel to an oil-lifting line. By means of an electric connection provided on the outside of the oil pan module, said oil pump can be connected with and supplied by the electrical system of a motor vehicle (12-volt network). Besides the electric oil pump, a suction fitting extends into the oil pan module. Above the floor of the oil pan module, the suction fitting is closed by a screen-like insert. Through this insert, the lubricant supply 7 held in oil pan module 21 is aspirated. The cross-sectional surface area of the suction fitting can vary, namely it can decrease continuously in the direction of the suction side of the oil pump.
According to the process for fabricating an oil pan module, which is also disclosed as part of the invention, said oil pan module can be made of a thermoplastic material as an injection-molded part using a one-component or multicomponent injection-molding process. An oil pan module fabricated in this manner is provided with outer and inner reinforcing ribs injection-molded to it. The oil filter housing, sealing surfaces, reinforcing ribs and suction fitting can be integral with the oil pan module.
In a preferred process, the oil pan module is made of PA 6 or PA 661. This thermoplastic material contains glass fibers or mineral matter as fillers. By means of this material, the mechanical strength of the oil pan module is increased considerably, making it possible to meet special customer requirements concerning the strength of the plastic injection-molded oil pan. Another suitable thermoplastic material for injection-molding the oil pan module of the invention is high-impact polyamide.
1 PA=polyamide; PA 6=poly-caprolactam; PA 66=poly(1.6-hexamethylene adioamidexc3x97Translator